Integrated circuits contain many different layers of materials, including dielectric layers that insulate adjacent conducting layers from one another. With each decrease in the size of integrated circuits, the individual conducting layers and elements within the integrated circuits grow closer to adjacent conducting elements. This necessitates the use of dielectric layers made of materials with low dielectric constants to prevent problems with capacitance, cross talk, etc. between adjacent conducting layers and elements.
Low dielectric constant polymers have shown promise for use as dielectric materials in integrated circuits. Examples of low dielectric constant polymers include, but are not limited to, fluoropolymers such as TEFLON ((—CF2—CF2—)n; kd=1.9) and PPX-F ((—CF2—C6H4—CF2—)n; kd=2.23). Many of these materials have been found to be dimensionally and chemically stable under temperatures and processing conditions used in later fabrication steps, have low moisture absorption characteristics, and also have other favorable physical properties.
However, many low dielectric constant polymers have been found to adhere poorly to silicon-containing layers that are commonly used in integrated circuits, including but not limited to silicon oxide, silicon nitride, silicon carbide, and SiOxCyHz. For example, in single or dual Damascene processes, a feature (for example, a trench or a via) is etched in a dielectric layer, and copper is deposited in the etched feature. Copper is then removed from areas surrounding the feature by a chemical/mechanical polishing step. If the dielectric layer adheres poorly to the underlying layer, the etching, deposition, chemical/mechanical polishing, and/or other processing steps may cause the dielectric layer and the underlying layer to delaminate.
Furthermore, the syntheses used to create these polymer dielectric films may leave many unreacted free radical chain ends, which may be susceptible to contamination by water, oxygen, and other materials that may reduce the dimensional and chemical stability of the film under increased temperatures. These problems may result in unreliable device fabrication and low device yields.